Ingot molds used in the production of steel ingots usually consist of upright cast iron, box-like shells open at both ends. To close the bottom for casting steel therein, the mold is placed upright on a thick cast iron mold stool. Hence, an ingot mold cavity is formed by the mold stool on the bottom and the interior side-walls of the ingot mold thereover. A reasonably close fit between the mold and stool should be assured to prevent leakage of molten steel therebetween.
Ingot molds and mold stools are usually manufactured in accordance with established sand-mold foundry techniques. While molding techniques for the manufacture of ingot molds has undergone some refinements, such as chill casting procedures, mold stools are still usually produced by conventional age-old foundry practices. Specifically, a rectangular molding flask is placed over and clamped to a rigid molding plate to form an open-topped box-like structure. Molding sand is then spread over the inside bottom to a depth of several inches, and then compacted to form a flat sand surface. A rectangular pattern, usually made of wood, is then placed on the flat sand surface such that there is several inches of clearance between the sides of the pattern and the flask walls. Molding sand is then compacted into that space. The pattern is then carefully removed to leave a rectangular cavity in the molding sand. A pouring gate must also be provided in the molding sand adjacent to the cavity to funnel molten cast iron to the bottom of the cavity. After the mold stool has been cast in the cavity and solidified, the cast metal is removed from the sand mold, the gate broken-off and the surfaces cleaned. Surface cleaning is usually performed by hand, using a pneumatic chipper to scrape-off the molding sand adhering to the as-cast surface.